Vaccination is the most cost effective means of preventing H. influenzae type b (Hib) disease. Newly developed Hib polysaccharide-protein conjugate vaccines being tested are effective in children 2 months and older. However, some infants may be incapable of responding to polysaccharide antigens. A 16,000 dalton OMP has been identified as a potential vaccine candidate, has been found in all Hib isolates tested, and is antigenically conserved among Hib strains. The 16K OMP constitutes approximately 1.5% of the total OMP's, making it difficult and expensive to purify commercially. These studies will facilitate production of large amounts of the protein for use as a vaccine. This would be the first use of a protein vaccine against Hib disease. These studies will take recombinant plasmids encoding the putative 16K OMP gene in Escherichia coli and attempt to overexpress the gene product under the control of a regulatable promoter. Immunogenicity of the cloned protein will be examined using both bactericidal assays and animal protection studies. Phase II studies will be development of procedures amenable to large scale purification of the cloned protein and additional testing of immunogenicity.